Simultaneous Measurement and Modeling of MDOF Static/Thermal Errors of CNC Machine Tool Rotational Axes

Existing measurement and modeling methods for CNC machine tool rotational axis errors only considered the influences of multiple degrees of freedom(MDOF) static geometric errors or single degree of freedom thermal errors acting in isolation without accounting for the coupled effects, a simultaneous measurement and modeling for MDOF static/thermal errors in CNC machine tool rotational axes was proposed based on a double ball bar. Firstly, a model was developed to describe the variation in length of the double ball bar using homogeneous coordinate transformation. A static/thermal error identification model was constructed by solving a system of nonhomogeneous linear equations based on this model. Subsequently, to minimize the influences of thermal dissipation on the measurement results, a specific installation mode adapted to the simultaneous measurement of MDOF static/thermal errors was designed to reduce the installation time of the double ball bar. Additionally, a prediction model for MDOF static/thermal errors in rotational axis was established using a CNN-LSTM. Finally, experiments were conducted on the C-axis of a gear grinding machine to rapidly identify the rotational axis errors at various speeds. The accuracy of the prediction model was verified by utilizing the static/thermal error model to predict the errors of C-axis and the variation in length of the double ball bar. © 2024 Chinese Mechanical Engineering Society. All rights reserved.